text: 
  
  import { Component } from 'react';
  
  import React, {
    StyleSheet,
    View,
    Dimensions,
    Text,
    PixelRatio,
    TouchableHighlight,
    TouchableOpacity,
  } from 'react-native';
  var cssVar = require('cssVar');
  
  export default NavigationBarRouteMapper = {
    LeftButton: function(route, navigator, index, navState) {
      if (index === 0) {
        return null;
      }
      var previousRoute = navState.routeStack[index - 1];
      return (
        <TouchableOpacity
          onPress={() => navigator.pop()}
          style={styles.navBarLeftButton}>
          <Text style={[styles.navBarText, styles.navBarButtonText]}>
            {previousRoute.title}
          </Text>
        </TouchableOpacity>
      );
    },
    RightButton: function(route, navigator, index, navState) {
      return  null;
    },
    Title: function(route, navigator, index, navState) {
      return (
        <Text style={[styles.navBarText, styles.navBarTitleText]}>
          {route.title}
        </Text>
      );
    },
  
  };
  
  
  
  
  var styles = StyleSheet.create({
    messageText: {
      fontSize: 17,
      fontWeight: '500',
      padding: 15,
      marginTop: 50,
      marginLeft: 15,
    },
    button: {
      backgroundColor: 'white',
      padding: 15,
      borderBottomWidth: 1 / PixelRatio.get(),
      borderBottomColor: '#CDCDCD',
    },
    buttonText: {
      fontSize: 17,
      fontWeight: '500',
    },
    navBar: {
      backgroundColor: '#e3e3e3',
    },
    navBarText: {
      fontSize: 16,
      marginVertical: 10,
    },
    navBarTitleText: {
      color: cssVar('fbui-bluegray-60'),
      fontWeight: '500',
      marginVertical: 15,
    },
    navBarLeftButton: {
      paddingLeft: 10,
    },
    navBarRightButton: {
      paddingRight: 10,
    },
    navBarButtonText: {
      color: cssVar('fbui-accent-blue'),
    },
    scene: {
      flex: 1,
      paddingTop: 20,
      backgroundColor: '#EAEAEA',
    },
    container: {
      flex: 1,
      backgroundColor: 'white',
    },
    toolbar: {
      backgroundColor: '#e0e0e0',
      height: 56,
    },
  });
  
  
  